This invention relates to well tools, and more specifically to casing hanger running tools for use in underwater oil and gas wells. In particular, the invention relates to hydraulic operated well tools for running, and landing underwater casing hangers without having to rotate the running string.
For many years it has been common practice in the oil and gas industry to run and land underwater well casing hangers by means of a tool that is threaded to the hanger, and that is released from the hanger by rotation of the tubular running string, such as a string of drill pipe, at the surface. However, practical that may be in some instances, past experience has proven that it is often difficult and undesirable in deep water drilling to rotate the running string, especially where high torques must be applied to the string in order to perform downhole operations.
Numerous attempts to overcome this problem have been devised, but none has been found completely satisfactory. For example, U.S. Pat. No. 3,827,488 to Piazza et al discloses a casing hanger assembly that is threaded onto a running tool, and in order to release the tool from the hanger assembly the running string must be rotated. Another type of casing hanger apparatus for use in underwater wells is shown in U.S. Pat. No. 3,885,625 to Ahlstone, but here again the hanger is connected to the tool only by threads, thereby necessitating rotation of the running string to disengage the tool from the hanger. Still another system for running and landing a casing hanger assembly in an underwater well is described in U.S. Pat. No. 3,897,823, also to Ahlstone, and although hydraulic pressure is employed to actuate a packing in the wellhead, the running string must be rotated to release the running tool from the hanger.
In U.S. Pat. No. 3,543,847 to Haeber, there is disclosed a casing hanger and running tool combination that employs hydraulic pressure to release the tool from the hanger. However, the tool and hanger are interconnected by a complex system of locking dogs, springs, and dog cage that are expensive to manufacture and relatively highly vulnerable to damage and malfunction.